(a) Field of the Invention
The present invention relates to a thin film transistor (“TFT”) array panel and a manufacturing method thereof. More particularly, the present invention relates to a TFT array panel having improved contact characteristics between a signal line and an upper layer, and a manufacturing method of the TFT array panel.
(b) Description of the Related Art
Flat panel displays such as a liquid crystal display (“LCD”) and an organic light emitting diode (“OLED”) display include several pairs of field generating electrodes and electro-optical active layers interposed therebetween. The LCD includes a liquid crystal layer as an electro-optical active layer, and the OLED includes an organic emission layer as the electro-optical active layer.
One electrode of a pair of field generating electrodes, i.e., a pixel electrode, is commonly connected to a switching element for transmitting electrical signals to the pixel electrode, and the electro-optical active layer converts the electrical signals to optical signals to display an image.
A thin film transistor (“TFT”) having three terminals is used for the switching element in the flat panel display, and a plurality of signal lines such as gate lines and data lines are also provided on the flat panel display. The gate lines transmit signals for controlling the TFTs and the data lines transmit signals applied to the pixel electrodes.
Wiring made of a material having low resistivity, such as aluminum (Al), is commonly used for the signal lines of the flat panel display.
However, a signal line made of aluminum has a poor contact property with other materials such as indium-tin-oxide (“ITO”) and indium zinc oxide (“IZO”), and thus a pixel electrode of ITO or IZO in direct contact with the aluminum signal line may receive imperfect signals from the aluminum signal line.
Accordingly, for improving the contact property between the signal line made of aluminum and the upper layer made of ITO or IZO, it is known that the signal lines have a multi-layered structure including a lower layer of aluminum and an upper layer covering the lower layer of aluminum and made of a material such as a molybdenum (Mo)-containing metal, chromium (Cr), tantalum (Ta), or titanium (Ti), which has good physical, chemical, and electrical contact characteristics with other materials such as ITO or IZO.